Structuring of binary PP/PA‐6 blends and ternary PP/PA‐6/GF blends

Morphological development under shear flow conditions for binary polypropylene (PP)‐polyamide‐6 (PA‐6) and ternary PP‐PA‐6‐glass fiber blends has been investigated. The shear viscosity was determined at several temperatures, and the blend morphology was investigated as a function of shear rate and temperature. Blend morphology perpendicular and parallel to the flow direction was examined to give a complete description of the structuring of the polymer blend during flow. For blends containing a PA‐6 matrix, the glass fiber (GF) and minor PP phase are separately dispersed within the matrix, and the morphological development during flow is similar for binary and ternary blends. However, for blends containing a PP matrix, the GF are mainly encapsulated by the minor PA‐6 phase. This encapsulated morphology reduces the effective amount of PA‐6 dispersed within the matrix, and the development of an “interlayer slip” morphology, typical of PP/PA‐6 blends, is reduced. These differing ternary blend structures have implications for the shear viscosity, and its correspondence to a rule of mixtures prediction. For PA‐6–rich blends, the actual viscosity is lower than the predicted, owing to slippage between the PP dispersed phase and the PA‐6 matrix. However, in PP‐rich ternary blends, the experimental viscosity data matches a modified rule of mixtures prediction. The addition of PA‐6 to a PP/GF system does not increase the amount of “slippage” sites, owing to the encapsulated morphology. Therefore, the shear viscosity is not reduced by PP‐PA‐6 slippage.